The gist is that INTP typically is an abstract modeller, whereas ENTP likes to tinker in reality and make things manifest.
ENTP engages the world in a back and forth, INTP explores the world to take knowledge back inside for the model(s).

Typical problem for INTP is detaching too much from the world and desires, whereas ENTP is more likely to struggle with self-indulgence.

The two common functions are Ti and Ne.
When Ti is primary (INTP), Ne is used to bring back information for Ti to use much like a dog bringing back bones.
When Ne is primary (ENTP), Ti helps create and secure footing as the ENTP springs from one Ne connection to the next.

It's kind of hard to answer the question succinctly, since there are various types of INTPs, ENTPs, and un-health.

"Hey Capa -- We're only stardust." ~ "Sunshine"

“Pleasure to me is wonder—the unexplored, the unexpected, the thing that is hidden and the changeless thing that lurks behind superficial mutability. To trace the remote in the immediate; the eternal in the ephemeral; the past in the present; the infinite in the finite; these are to me the springs of delight and beauty.” ~ H.P. Lovecraft

There's this theory that unhealthy types are made up with a negative dominant function, an ignored auxiliary, a bossy tertiary and an immature inferior...
So for an ENTP you'll get a Ne + Fe + a little bit of whiny Si; while for an INTP you'd get a Ti + Si + some Fe...

I've known someone who more or less fits this unhealthy ENTP description. He's a genius and narcistic. He needs constant praise for his awesome ideas, using Fe rather than Ti to check their worth; but his Fe is lacking the other direction of working. Others have to respect his feelings, but the other way around isn't necessary. Si sometimes crops up in details which "should be done this way" without any reason.
I don't know any unhealthy INTP examples.